[If you don't feel like reading about anaemia in oncology patients, here's another pic of Randy].

A timothy-hay house acts simaltaneously as a shelter and a snack.

Cushing enjoys the house too.

Anaemia is a problem in
cancer patients for a range of reasons. It is associated with a poorer overall
prognosis, as well as poor wound healing, decreased appetite (especially in
cats), increased anaesthetic and surgical risk and increased risk of toxicity
associated with chemotherapy or radiation. The aim is to avoid it, or recognise and treat anaemia where necessary.

The most important thing I
learned (well, I knew it but it was reinforced) is that cancer patients develop
anaemia for a variety of reasons which can be categorised under:

Decreased production of
red blood cells (this is the most common form)

Increased loss

Increased destruction

Decreased production

Anaemia of chronic disease
is the most common form of decreased production in the cancer patient and is
usually mild. It usually causes a non-regenerative, normocytic, normochromic
anaemia.

Myelophthisis (bone marrow
suppression due to marrow infiltration by tumour cells with local production of
myelosuppressive cytokines) is more common in dogs than cats, and tends to be
seen with lymphoid tumours and leukaemias. This can vary from mild to severe.
Red blood cells are often the last cell line to decrease, with
thrombocytopaenia often occurring in the early stages. It causes a non-regenerative,
normocytic, normochromic anaemia, as does chemotherapy associated anaemia.

Iron deficiency anaemia is
uncommon but usually secondary to gastrointestinal or external blood loss that
is ongoing and severe. It causes a non-regenerative, microcytic, hypochromic
anaemia.

Increased loss

This is most common with
vascular tumours such as Haemangiosarcoma and haemangiomas. Any splenic tumour
has a very high risk of bleeding and most have at least one haematoma
associated with them. Hepatic tumours can also bleed. Clinical signs can be
cyclical as the animal has an internal bleed then autotransfuses over 3-4 days,
hence they can appear weak and lethargic and bounce back. Autotransfusion
itself can cause red blood cell changes, e.g. schistocytes.

Initially animals with
anaemia secondary to vascular tumours will have a non-regenerative, normocytic,
normochromic anaemia, but over time this can become regenerative, with
macrocytosis, polychromasia an reticulocytosis (though autotransfusion can
blunt the regenerative response).

Blood loss commonly occurs
in the GIT, with epithelial tumours bleeding the most. Melena is not always
seen or recognised by owners. Around 5-10 per cent of dogs with mast cell
tumours will have gastrointestinal ulcers, but significant bleeding will only
occur in a fraction of these. Other potential causes of GI ulceration include
gastrinomas, renal failure and liver failure (lymphoma a common culprit).
Animals with nasal tumours may swallow blood, so epistaxis isn’t always
present. It can be tricky in some cases to differentiate nasal from
gastrointestinal bleeding.

Usually the signs of the
tumour will predominate over signs of anaemia – for example, with GIT tumours,
the predominant signs will be vomiting, diarrhoea and weight loss. These
animals may have a moderate to severe hypoproteinaemia.

Primary and secondary
coagulopathies can occur. Immune mediated thrombocytopaenia is often associated
with lymphoma. Dogs with haemangiosarcoma are at increased risk of disseminated
intravascular coagulation (DIC) – strangely enough DIC (or IC at any rate) can
be localised to the spleen. Mast cell tumours produce anticoagulant factors
such as heparin.

The anaemia is usually
regenerative.

Increased destruction

The main causes in cancer
patients are immune-mediated haemolytic anaemia (IMHA), microangiopathic
haemolytic anaemia and erythrophagocytosis.

IMHA is a common cause of
severe anaemia in cancer patients and is most often associated with lymphoid
malignancies. The aetiology is not fully understood but it might be due to
altered immune function or the presence of surface antigens on tumour cells
that are shared by red blood cells. It usually causes regenerative anaemia. Quite
often in these cases the animal will present for signs of anaemia and the
cancer is discovered during work up, rather than the other way around.

Microangiopathic
haemolytic anaemia is most often seen with vascular tumours such as
haemangiosarcomas, but it can be seen with lymphoma. Red cells cop a beating
when they pass through vascular channels containing fibrin strands, and these
damaged cells are removed by the spleen. Dr Bennett said there is probably also
an immune-mediated component. There is a regenerative anaemia, often with signs
of erythrocyte damage e.g. schistocytes.

Erythrophagocytosis is
seen with the aggressive form of histiocytic sarcoma. Bernese Mountain Dogs are
over-represented here. As the name suggests, the cancer cells actually
phagocytose (eat) red blood cells. It causes a severe regenerative anaemia.

What do you do about it?

The trick can be working
out which kind of anaemia the patient has. Small tumours can be associated with
severe anaemia and large tumours can be associated with mild anaemia – or vice
versa. The presentation of the animal depends on the tumour type, stage and
grade.

Obviously the first step
is to identify anaemia (low haematocrit and haemoglobin), but also find out in
the history whether onset is acute or chronic. Have there been signs of
lethargy, pallor, weakness, exercise intolerance, reduced appetite, dyspnoea?
For how long? Have there been episodes of external blood loss?

Signs to look for on
physical exam include obvious signs of external haemorrhage, a fluid wave,
muffled ventral lung/heart sounds, pallor or signs of coagulopathy. Mast cell
tumours may be associated with gastric ulceration, so cutaneous tumours can be
an important clue in the work up of anaemia.

A rectal exam should be
performed to check the faeces and rectal mucosa for blood. I knew that recent
(ie within 4 days) ingestion of meat could interfere with occult faecal blood
test results – but ingestion of green vegies in the same time period can also
give a false result.

A CBC/MBA and UA should be
performed, but its always important to perform a blood smear for morphological
evaluation.

Treatment of anaemia
depends on the severity and the underlying cause. Ideally, we diagnose and
eliminate the underlying cause (for example, remove the bleeding tumour). Other
treatment may include blood or platelet rich plasma transfusion, oxygen, rest,
gastroprotectants, vitamin K, withdrawal of certain drugs from the treatment
regime or immunosuppression – depending on the particular case.

Withdrawal of chemotherapy
drugs should be carefully considered as it brings the risk of disease relapse.
Use of an alternate agent can be considered although it is likely to have
similar effects, or EPO can be given (though Dr Bennett doesn’t feel this
really helps in most cases).

Veterinary Ethics: Navigating Tough Cases

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